DESCRIPTION: The longevity of HIV infected individuals (HIV+) has been extended by new therapies, but the disease still follows a progressive course with significant deleterious effects on the brain. High comorbidity with alcohol abuse among HIV+ individuals puts dually afflicted patients at risk for additive or synergistic effects, especially in frontostriatal brain systems that control executive and motor functions. Recent advances in magnetic resonance (MR) imaging, such as MR spectroscopy, MR diffusion tensor imaging, provide new opportunities to study, in vivo, the macrostructural, microstructural, and biochemical bases of the pathophysiology of HIV infection and alcohol abuse. Further, these techniques enable the observation of disease-induced changes over time, and the degree to which these changes relate to clinical state and cognitive and motor performance. In balanced four group, we will compare high and low alcohol consuming HIV+ patients with low-alcohol consuming HIV- subjects over a three year period in a naturalistic design to model the cumulative and progressive deleterious effects on the brain of combined HIV infection and alcohol abuse. We will test dual model of their comorbidity: interactive effects on structures disrupted by both disease (e.g., basal ganglia in HIV+). Three specific aims are proposed: Specific Aim 1: To use neuroimaging and neuropsychological measures to establish patterns of normality and abnormality in HIV+ alone, alcohol abuse alone, and HIV+ with alcohol abuse. Specific Aim 2: To track in neuroimaging measures at 1 and 3 year follow-up sessions. Specific Aim 3: To establish cross-sectional and longitudinal within-subject relationships among nueroimaging, neuropsychological, and clinical measures.